There are many instances in which it may be desirable to eliminate or reduce light from entering a room through a window or a skylight. A dark room, a conference room utilized for film viewing, or a chemical laboratory in which a light-sensitive experiment is to be conducted are just a few examples of the applications of operable flexible shade systems. Typically, the shades of operable shade systems are unrolled from a roller residing within a top casing affixed to the top of the wall opening (window, skylight and the like) and the sides of the shade are slidably movable within channels formed by the side casings of the shade system. The side casings are affixed to the sides of the wall opening. The channels in the side casings guide the shade when being raised or lowered and also assist in making certain that the shade, when fully lowered, results in complete coverage of the wall opening.
Numerous variations in commercially available operable shade systems are known in the art. The system's roller may be actuated by an electric motor disposed within the top casing, a manually operated crank, or a bi-directional clutch having a chain affixed thereto. The shade may be comprised of various materials having varied textures and light admitting properties. In this manner, the wall opening may be made opaque, semi-transparent, or transparent when covered by such a shade. Representative of operable shade systems are the FlexShade Systems, both motorized and manually operated, available from Draper Shade and Screen Co., Inc. of Spiceland, Ind.
For many installations of operable shade systems, and especially for those installations in which a positive pressure may exist in the room having the wall opening to be covered by the shade, a retention system is provided to ensure that the edges of the shade remain within the channels of the side casings when reasonable pressure is applied to the shade. In one such retention system, horizontally oriented spring steel stays of a length less than the width of the shade are affixed to the shade at spaced intervals along the length of the shade. Specifically, each stay is attached to the shade with a double-sided adhesive, and a fabric covering having dimensions slightly greater than that of the stay is attached to the shade and the stay by use of a double-sided adhesive tape. Another known retention system utilizes grommets which are inserted through the shade along the shade's side edges at spaced intervals.
For both the above-described prior art retention systems, the edges of the shade are placed within channels in side casings installed in the wall opening. This provides some assurance that the shade will cover the opening in the event that pressure is applied to the shade. However, if significant force is applied to either retention system, the edges of the shade have been known to come out of the channels, thereby defeating the purpose of the shade by allowing light to pass through the edges of the shade. For example, the edges of a shade using the steel stay retention system may slip out of the channels if the stays are bent a substantial amount, and the fabric of a shade having grommets on the shade's edges may actually be torn when pressure is applied to the shade, thereby allowing the shade to become free of the channels. Therefore, it is desirable to provide a retention system for such shades which is better able to withstand the application of a force to the shade by ensuring that the edges of the shade remain within the side channels.
A retention system having steel stays is further disadvantageous because the number of stays required to secure an unrolled shade within the side channels results in a rolled shade which is of a diameter which may require the use of a larger top casing than may be desirable. Further, affixing the stays and fabric coverings to the shade by an adhesive may permit the stays to become dislodged from beneath the fabric covering. The retention system having grommets presents another problem as the fabric must be punctured for the introduction of the grommets into the shade. This weakens the shade's fabric and may tear the fabric near each grommet. Therefore, it is desirable to provide a retention system for flexible shades which reduces the size of the shade when rolled and which does not weaken the shade's fabric at various points along the edges of the shade. It is also desirable to reduce the manufacturing costs of the shade system when compared to prior art.
Yet another problem associated with the shade systems using either stays or grommets is the width of the channel required to secure the edges of the shade within the channel. Typically, the greater the width of the shade, the wider the channels must be. For example, a three (3) inch channel width may be required for shade widths of up to 72 inches, a four (4) inch channel width may be required for shade widths from 72 inches to 96 inches, and a five (5) inch channel width may be required for shade widths greater than 96 inches. The channel width's dependence on shade width is based in part on the retention system's resistance to positive pressure coupled with the limitation on the number of grommets or stays that may be utilized without adversely affecting the diameter of a completely rolled screen. Wide channels necessitate wide side casings which detract from the appearance of the window or skylight in which the shade is installed and also limit the amount of light entering the window or skylight when the shade is completely rolled up and not in use. It is therefore desirable to provide a retention system which utilizes narrower channels than that required for the prior art and which can be used with a constant channel width over a greater range of shade lengths.